Device for the screening of liquids



May 2, 1967 E. G, R. RANHAGEN ETAL 3,317,051

DEVICE FOR THE SCREENING OF LIQUIDS Filed June 17, 1964 United States Patent O 3,317,051 DEVICE FOR THE SCREENING OF LIQUIDS Ernst Gustaf Rane Ranhagen and Erik Gustaf Ranhagen, Danderyd, Sweden, assignors to Aktiebolaget Karlstads Mekaniska Werkstad, Karlstad, Sweden, a jomt-stock company of Sweden Filed June 17, 1964, Ser. No. 375,881 Claims priority, application Sweden, June 19, 1963, 6,845/ 63 3 Claims.V (Cl. 210332) The present invention relates to improvements inscreens for liquids and in particular replaceable screens or filter elements intended for screening, fractionating, filtering or dewatering liquid suspensions. Although the invention may be applied to a great number of different industrial processes, it is particularly applicable in the cel-lulose and paper industry where one often faces the problem to screen, filter, fractionate or dewater `fibers or other coarse particles suspended in water.

Devices of this kind, known prior to this invention, have all had some drawbacks with respect to costs, space requirements, tendency for clogging and the difficulty to replace damaged or worn-out screen elements in an easy manner.

The object of the present invention is therefore to provide a screen which is simple and inexpensive and which has a reduced tendency to clog whereby the relation between screen surface and the amount of liquid that may be screened per unit of time may be made smaller so that,

for a given capacity, an .apparatus according to the invention will require -less space.

Another object of the invention is to provide a screen which is easily replaceable.

These other objects of the invention are mainly realized in that the filter comprises a substantially rectangular or trapezoid screen, manufactured from a comparatively thin, perforated, stiff but resilient sheet material, adapted to be springingly inserted between a pair of elongated holder elements provided with longitudinal grooves adapted to receive opposite edges of the filter element. The filter element is thereby retained between the holder elements due to its stiffness.

According to a further embodiment of the invention Ythe filter element may lbe manufactured from expanded sheet metal and it may preferably be arranged between the holder elements in such a way that its convex side faces the direction from which the fluid to be screened is supplied.

Other details of the invention will be evident from the following description.

'I'he invention will now be further described with reference to the accompanying drawing which by way of an example show an embodiment of the invention.

FIG. l shows in longitudinal section a coarse Screener, for example for cellulose fibers, and,

FIG. 2 shows a detail `of the apparatus according to FIG. in section along the line A-A.

The apparatus shown in FIG. 1 comprises a so-called spiral sprinkler arranged to cooperate with the screening elements according to the invention. The coarse screener comprises therefore a sprinkler or sprayer pipe consisting of an inner shell 1 and an louter shell 2. The inner shell 1 is, at one of its ends, by means of an axis 3 connected to suitable driving means so that it may be made to rotate with respect to the other shell. In the embodiment shown the sprayer pipe is substantially concentrically located within a casing 4 which casing is provided with removable and fixed end walls 15 and 16 respectively.' The inner shell 1 is provided with a plurality of helical slots 7, 7 and the outer shell 2 is also provided with slots, for example with helical slots having an op- "ice posite pitch so that the slots in the outer and inner shells intersect thus providing openings to the compounded shell. The space between the outer sheel 2 and the inner surface of the casing 4 is by means of a plurality of screens or filters 9 divided into two from each other separated chambers 10 and 11.

The device works in the following manner. The liquid which is to be screened or filtered with respect to solid suspended material, for example fibres or the like, is fed under suitable pressure through the inlet 8 which communicates with the fixed outer shell 2. The shell 1 may preferably be provided with slots along its entire length and manufactured from a suitable resilient material so that it, by means of the fiuid pressure is pressed against the inner `surface of the outer shell causing the two shells to seal against each other. At those locations where the slots intersect they will define openings in the compounded shell through which the liquid may be sprayed in the form of substantially -radially outward directed jets.

By rotating the shells with respect to each other the jets can be made to travel upwards or downwards and their place of impact on the screen or filter will vary accordingly. Finer material such as fines, krills or the like together with the liquid will hereby pass through the filter or screen and may be extracted through the outlet 12 while coarser material, for example cellulose fibers together with the remaining liquid, usually water, may be extracted through the outlet 13.

FIG. 2 shows filter elements according to the invention which are particularly suitable for use together with the sprayer pipe capable of generating outwardly directed movable jets for example a sprayer pipe of the kind described above, but may of course also be used together with conventional sprayers. In the walls of the casing 4 longitudinal ribs 14 are provided which ribs for example may be secured to the walls by means of threaded bolts 15. Each rib is near its free edge provided with longitudinal grooves 16. Between any two of these ribs is a filter or screen holder 17 inserted which may |be manufactured from a perforated, slotted resilient sheet metal and arranged in such a way that it, due to its resiliency, remains fixed in its position between the slots. The holder 17 may lalso be provided with a screen or filter cloth 18 which is held between the holder and the ribs. The screen :and holder may also be combined into one element which preferably may be manufactured from sheet metal of the so-called expanded metal kind.

A screen element of the kind described is in addition to being cheap and easily replaceable, also, as shown in FIG. 2, shaped in such a way that its surface presents varying angles with the fluid jets as they move in the peripheral direction. This is shown in FIG. 2, where the screening elements '17, 18 have their concave side facing in the direction from which the fluid jets issue. The fluid jets will thereby flush away dewatered material which may stick to the surface of the filter element.

Another advantage of the filter element is that it can be manufactured from comparatively thin material and still, due to its bending, be sufficiently rigid. Because the fluid jets move along the surface of the screen or filter element this surface will be kept clean in an efficient way and a risk for clogging caused to remaining material on the filter element is considerably reduced. The jets will namely as mentioned above spray or fiush away the dewatered material and, at the same time, they may initiate vibration in the filter element which has proved very advantageous for keeping the filter element clean.

When the filter described above is used together with the apparatus according to FIG. 1 the ribs 24 preferably are provided with channels or holes 18, as indicated in the drawing, which allow the fluid to pass between the diffe-r- 3 ent chambers 11 so that it finally can issue out to the outlet 13.

Although the iilter has been described together with the particular kind of the apparatus it should be lobvious to one skilled in the art that since it allows higher specic load per unit surface and has very little or no tendency to clog and further is cheap and easy to replace, it should be very advantageous as a substitute for conventional lter in drum `dewaters which hitherto have been heavy and required considerable room.

It should also be obvious for one skilled in the art that the filter described might be particularly suitable for various applications for treating suspensions in the low concentration range.

In addition to this the filter is particularly suitable for liber sorting or fractionating in the paper and cellulose industry, for example for the removal of ray cell fibers and ber fragments, for de-inking and de-pithing, for the removal of annual plant 'ores from pulp and for sorting mechanical pulp in a plurality of fractions.

What is claimed is:

1. A liquid screening device comprising a substantially impervious cylindrical, substantially vertical, stationary casing adapted for containing a centrally located spraying device capable of generating outwardly directed movable jets, a plurality of elongated holder means arranged along the inner wall of said cylindrical casing substantially parallel to its longitudinal axis, said holder means being provided with longitudinal grooves, a plurality of filter screens having opposite edges received in the grooves of adjacent holder means, each filter screen being constituted as a comparatively thin perforated, stil ibut bendable sheet material, said ilter screens being wider than the linear distance between adjacent holder means to be secured there'between in flexed condition with convex sides facing inwardly towards the centrally located spraying device to define enclosed spaces between the inner surface of the casing and the concave surface of the lter screens, means for extracting liquid from said spaces .and means for extracting liquid from the spaces between the spraying device and the screens, and a further screening element on said screens retained between the screens and the holder means.

2. A liquid screening device as claimed in claim 1, in which the screen is expanded sheet metal.

3. A liquid screening device as claimed in claim 1 in which the holder means comprise rib elements provided with said longitudinal grooves, said rib elements being provided with openings therethrough allowing liquid to flow between the spaces enclosed between adjacent screens,

their associated rib elements and the wall of the casing.

References Cited by the Examiner UNITED STATES PATENTS 1,870,442 8/1932 Coley 210-403 X 1,963,610 6/1934 Bescraft 210-404 X 2,289,411 7/1942 Denhard et al. 21o-404 2,454,134 11/1948 Burleson 210-404 FOREIGN PATENTS 725,333 3/ 1955 Great Britain.

REUBEN FRIEDMAN, Primary Examiner. F. MEDLEY, Assistant Examiner. 

1. A LIQUID SCREENING DEVICE COMPRISING A SUBSTANTIALLY IMPERVIOUS CYLINDRICAL, SUBSTANTIALLY VERTICAL, STATIONARY CASING ADAPTED FOR CONTAINING A CENTRALLY LOCATED SPRAYING DEVICE CAPABLE OF GENERATING OUTWARDLY DIRECTED MOVABLE JETS, A PLURALITY OF ELONGATED HOLDER MEANS ARRANGED ALONG THE INNER WALL OF SAID CYLINDRICAL CASING SUBSTANTIALLY PARALLEL TO ITS LONGITUDINAL AXIS, SAID HOLDER MEANS BEING PROVIDED WITH LONGITUDINAL GROOVES, A PLURALITY OF FILTER SCREENS HAVING OPPOSITE EDGES RECEIVED IN THE GROOVES OF ADJACENT HOLDER MEANS, EACH FILTER SCREEN BEING CONSTITUTED AS A COMPARATIVELY THIN PERFORATED, STIFF BUT BENDABLE SHEET MATERIAL, SAID FILTER SCREENS BEING WIDER THAN THE LINEAR DISTANCE BETWEEN ADJACENT HOLDER MEANS TO BE SECURED THEREBETWEEN IN FLEXED CONDITION WITH CONVEX SIDES FACING INWARDLY TOWARDS THE CENTRALLY LOCATED SPRAYING DEVICE TO DEFINE ENCLOSED SPACES BETWEEN THE INNER SURFACE OF THE CASING AND THE CONCAVE SURFACE OF THE FILTER SCREENS, MEANS FOR EXTRACTING LIQUID FROM SAID SPACES AND MEANS FOR EXTRACTING LIQUID FROM THE SPACES BETWEEN THE SPRAYING DEVICE AND THE SCREENS, AND A FURTHER SCREENING ELEMENT ON SAID SCREENS RETAINED BETWEEN THE SCREENS AND THE HOLDER MEANS. 